Homebrew 5L mini Keg

So I have been homebrewing for a few years now, and I’ve started a little project that thought I would share it here in case anyone who is getting into homebrewing, or wants to, might save some time and money by skipping some of the purchases I have made and things I’ve done.

I’ll be posting this in parts for my own sanity, but also so that it is easy to skip parts you aren’t interested in/already know… because I ramble!

The “problem” - As if beer was ever a problem…

So far I have used mostly glass bottles for storage and serving, but I also have in my arsenal, a large 5gallon plastic pressure barrel, and a small plastic bottle keg system (Tap-A-Daft).

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I would love to use bottles less, and the kegs more, but all three have their pros and cons and the cons of the kegs slightly outweigh the cons of the bottles:

Bottle Pros: Easy to transport, easy to refrigerate, great for preserving quality (beer is well protected from oxygen and so on) and unopened bottles remain protected, a cheap solution (initial outlay of enough bottles for a 5gallon batch costs under £25, and the caps to go on the top are around 50p per batch), and easy to replace (if a single bottle breaks it’s not a big deal), can mix-and-match bottles for batches, and easily take a variety of homebrews to parties

Bottle Cons: VERY time consuming and awkward to fill, take up a lot of storage space

5gal Keg Pros: VERY easy and quick to fill, takes up a small amount of space

5gal Keg Cons: difficult to transport and share, almost impossible to cool without dedicated fridge, co2 bulbs are required to pressure and protect contents (2 or 3 bulbs per batch at around £1ea), lots of failure points (rubber gets old and brittle, taps difficult to sanitize well, etc), if it breaks the whole system is gone, can only really store an entire batch in it, concerns about decrease in quality of beer after first pour (oxygenation, sanitization, general age, etc) and 5gallons of beer can take a long time to drink

5L plastic keg Pros: Easy and quick to fill, great for parties, possible to chill in large enough fridge, space saving (less space than bottles but more than 5Gal keg), can mix-and-match with bottles so can have different beers in different kegs, quality of beer is less of a concern as 5L takes no time at all to consume even for myself, and unopened kegs remain protected

5L plastic Keg Cons: Not readily available in the UK, so hard to replace and get parts for, only own 1 tap so can’t serve more than 1 beer at a time, and the tap (even if I can find it) costs ~£50!!

Essentially bottles are my preferred method, but they are a faff. The 5Gal keg would be awesome if I knew it would get drank quickly every time but it doesn’t so is basically a party keg. And I would love to just expand my 5L keg collection, but the tap is prohibitively expensive, and the parts (spare bottles, caps for bottles, etc) are neigh on impossible to get hold of, so, time to consider some other options…



So begins the search for alternative options for storing and serving my homebrew. There are some options I already had in mind, but I wanted to do a little research anyway.

Have you got the bottle?

The first idea that sprung to mind was to simply use larger bottles. Wine has been served from Flagons for thousands of years, and for hundreds Cider and Mead has been served from Flagons with sturdy corks. Modern versions exist in many forms too. There are traditional style cider flagons with pressure corks and caps, PVC versions with screw tops, and stainless steel growlers. All come in a variety of sizes at a variety of prices.

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The traditional shape PVC Flagons are affordable, and are generally around 2.5L and 5L. Sounds great – but they can be heavy and awkward to pour from when full, and their shape isn’t the most convenient for space saving storage even when empty. The stainless steel growlers are smaller (often small enough to fit in a fridge door) and slightly easier to store, but at a significant price hit. Both solutions are great for storing and carbonating just like a standard 500ml bottle, but realistically should only be opened if you know that all the beer will get drunk. Leftovers go flat and off pretty quickly. Also, these things aren’t easy to clean (although you can negate that by caring for them properly and cleaning immediately after use).

Oink oink

Another option I’ve been recommended to use in the past are alternatives similar to my 5L plastic kegs such as the beer box and, my personal favourite, the Party Pig. The two big advantages of the part pig are 1) the tap is MUCH cheaper, and 2) it uses an inflatable bag inserted into the keg which you inflate with air to keep the pressure up – no CO2 cost at all!

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However unfortunately while the taps are cheaper (less than a tenner), meaning I could have more beers on tap at once, the bottles themselves seem unproportionally expensive (over £25) which means the overall cost isn’t that great. Also… small point… I can’t find anywhere to buy from in England, and the shipping cost is astronomical so… back to the drawing board!

Easy Peasy

5L mini kegs (sometimes also called Easy Kegs) are an option I have considered many times. There are a few varieties available too. The main two versions are essentially with built in tap, or without. The most commonly available type is the version without the built in tap, which uses a top-tap system with a 8g CO2 build injector to pour the perfect pint just like from a larger commercial keg. The less common, but still readily available, version with the built in tap simply relies on a bung which has a valve on the top. Open the valve, pour your beer, simple as that.

These things are light weight, small enough to fit in fridges (sometimes admittedly with some rejigging of the shelves), a decent size for sharing, stack on top of one another when full and empty. They’re not super easy to clean, but again you can negate that by caring for them properly and cleaning immediately after use… seems like I’ve found a winner!!! Oh… but wait…

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Sadly there are downsides, and they’re pretty significant. The version without the built in tap has pretty much the same problem my plastic 5L kegs have – the kegs are cheap but the tap costs upwards of £40, so if I want to serve 3 beers simultaneously I will have to spend over £120 just on taps… The versions with the built in tap are much more affordable though right?! Less than £10 for a ready to go keg including tap and a way to let the beer flow since it’s gravity fed… however if any of you have tried those kegs from the supermarkets you will know, first of all the beer in the keg goes flat FAST. By the 3rd or 4th pint if you’re lucky . And on top of that, letting oxygen flow into your keg is not the best way to preserve your beer. Almost all the commercial ones warn that you should drink the beer within 2 days or risk drinking really rank beer. Fine for parties, not great for leftovers or drinking on my own.

I know my jokes are Corny

So at this point it looks like my reservations about cost might have to be put to one side. If large amounts of money are necessary anyway, lets consider a slightly more expensive option…

Corny kegs were originally used in pubs to serve soft drinks, but have been rapidly adopted by the homebrew scene. They some in two commonly available sizes (19L and 10.5L) which are pretty much perfect for standard whole or half homebrew batches, they are a completely closed system using CO2 to keep the keg under pressure and the drink protected from spoiling, they can be daisy-chained together for both larger batches and for filling smaller kegs from larger ones for taking to parties, the benefits go on and on.

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The two most significant down sides to Corny Kegs (and all similar growler and keg solutions) are Cost, and size. Essentially, the large kegs themselves are pretty expensive, anywhere from £50 to £100+ depending on condition, and a 19L (plus CO2, taps, and so on) isn’t easy to lug around to parties. So get a smaller keg… well, the kicker is that since most of the cost is related to the mechanics at the top of the keg (the CO2 and fluid out fittings, pressure rated lid, etc) the cost difference between the smallest available keg and the largest just isn’t that much. Even a small 5L keg costs £50+

On top of the keg cost, CO2 is an important factor. Most choose to gas their kegs with an s30 cannister, which is a larger 240g gas canister, which is more portable but adds weight and makes taking it to parties more cumbersome. Other options are to use a full “pub size” CO2 tank, which is more for the “serve from home” setup, or get an 8g/16g attachment for the gas in valve, but since you are pumping the beer up and out , defying gravity the entire time you serve, most people report they need quite a lot of CO2 bulbs to serve all of their beer.

As a long term homebrew setup solution, Corny Kegs are the way to go, and one day I will definitely invest in some and attach wall taps to my brewing shed. But right now it’s just not a viable option from cost alone, never mind considering factors of transportability and convenience.

Booze and Bicycles

Honestly the more research I did the more disillusioned I became. I simply didn’t have the money for the best setups, and the cheaper setups had drawbacks that simply outweighed any issues with my existing equipment.

I had almost given up on this whole idea, and was reserving myself to simply living what I had. My wife told me to treat myself to some booze to cheer myself up and while wandering around the supermarket I found a keg of Hobgoblin on offer… “Wow that’s almost as cheap as my homebrew! It’s a shame the mini keg with a tap is just gravity fed like these things, they would be perfect if there was some cheap and easy way to inject CO2 instead. Oh that reminds me, I need a new CO2 injector for my bicycle…”

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Now there’s a thought…

Final Method…



Easy Kegs with built in taps are cheap, easy, portable and a convenient size for sharing, but since they are gravity fed result in flat beer after a few pints, and spoilt beer after a couple of days.

Mini kegs with a separate tap attachment are also easy, portable and a convenient size for sharing, and are co2 charged resulting in protected, carbonated beer for extended periods of time, but the taps are very expensive making it impractical to serve multiple beers at once.

So I propose that there must be a way to safely charge Easy Kegs (with the built in tap) with co2, and that this should be achievable without spending large sums of money, allowing the serving of many beers at once for minimal financial outlay.



The first thing to do was to identify what kegs are actually available, and at what costs.

Buying a clean unused keg for around £8 and then experiencing issues would potentially mean a total loss of the funds spent. Knowing that I will almost certainly have some failures, my first plan was to buy a commercial filled keg with built in tap for £10 when on sale. This way even if I completely ruin the keg itself, or there are issues with the homebrew, at least I have still received something for the money spent (an extra £2 for 5L of beer has to be worth it).

The second thing to consider is how to charge the keg with co2, but there are a few important considerations:

  1. Pressure required
    It will be necessary to pressurise the barrel enough to retain carbonation, provide enough pressure to pour beer (until the keg is empty), and do this without making the keg explode…

  2. Pressure relief
    Since homebrew is very often conditioned (carbonation added) by adding sugar to the bottle/keg for the yeast to ferment, it is possible that the pressure might naturally be too great for the keg while it is full. Also, depending on how co2 is added to the keg, it will probably be possible to add too much. In either of these scenarios it will be important to be able to vert excess pressure, either manually or automatically.

  3. co2 source
    While large co2 cannisters tend to have convenient and abundantly availabble adaptors, since one of the main factors for this endeavour is transportability they would be both overkill and awkward. The co2 source should be enough to keep a keg or two pressurized until empty, but be small, and maybe detachable or not permanent.

  4. co2 Delivery method
    co2 delivery could either be automatic and regulated, like it is with larger systems, or manual. Automatic and regulated would require the source to be constantly connected which could be awkward depending on the co2 source chosen. Regulation might be possible with manual delivery, but is less important if the keg has a pressure release valve of some kind.

  5. Size and weight
    There would be no point in choosing a small 5L keg for transportability and with the desire to fit it in the fridge if the method for injecting co2 took up a lot of space or weighed a lot. Several lines with spliters or brass joints or whatever just wouldn’t be reasonable.

The "competition"

The existing solutions are essentially gravity fed supermarket kegs with built in taps, and easy kegs with a tap that is clamped to the top. Both solutions involve a bung in the top:
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The easy keg tap slips through a hole in the rubber bung, and simultaneously injects gas as you draw beer. The logic is that the pressure is regulated kind of automatically by the difference in pressure between the keg and the small co2 cartridge. This might be a little risky to assume when using a plastic build in tap which will introduce a point of weakness in the event of over-pressure.

The supermarket keg has a hinged flap on the bung, which you simply open each time you want to pour a beer.

Some research showed that you can, with a little (lot) of effort you can remove the bungs from most of the supermarket kegs, and the whole is exactly the same size as the easy keg. Some supermarket kegs have more complecated designs of both tap and bung, and these are probably best avoided.
You can buy a variety of replacement bungs for the easy kegs. The main types available are gravity feed bungs (left) which cost around 50p, rubber bungs with a removable center (middle) which cost around £1, and pressure relief bungs (right) which cost around £5
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All of these bungs are designed for the same size of hole, and would fit both the standard supermarket kegs (after original removal) and the easy keg.

With a little inginuity I should be able to adapt one of these bungs to have a valve of some sort that would be used to inject co2.

Valves, connectors and adaptors

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